Fastener assembly

ABSTRACT

A fastener assembly for securing a first panel member to a second panel member in a spaced-apart relationship. The fastener comprises a tubular shank portion having first and second end portions, a cavity being formed in the shank portion. A first spring member is secured on the outside of the shank portion and has openings near the first end of the shank portion to enable steel ball members to protrude therefrom. Inside the shank portion cavity is a stepped pin member that is spring loaded and held in place by a combination of the shank portion spring ball retention feature and step angles formed on the pin member.

.Iadd.This is a continuation of reissue application Ser. No. 08/433,671,filed May 4, 1995, now abandoned. .Iaddend.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements in assembly line typefastener assemblies wherein the fastener can be both quickly installedand released.

2. Description of the Prior Art

Many systems wherein at least two members are mechanically joinedrequire that the members be capable of being fastened together andseparated quickly and simply for maintainability purposes. For example,in the assembly of an automotive airbag to the steering column andwheel, the air bag mechanism typically is attached by four screws thatare threaded into tubular standoffs that are attached to a plate thatthe airbag is secured to. As the airbag is one of the last items to beassembled on the almost finished vehicle, its accessibility is verylimited. Therefore the time required to assemble the airbag to thesteering wheel assembly is longer than desired because the screws haveto be inserted from behind the steering wheel. The convenience ofinstallation is severely hampered due to the natural obstructions thataccompany any automobile such as a gear selector lever, the turn signalstalk, the steering wheel post shroud and the proximity of thedashboard. The installation may also require the steering wheel to berotated to a certain position in order to access all four holes; inaddition the aligning of the screw to its mating threads in a blindapplication is difficult. The same problems occur during the check outcycle of a malfunction occurs or at a later time during normal servicingat the dealer's facility. The current practice of locating the holes forthe airbag assembly and to install the four screws is slow andexpensive.

The reduction in time required to remove the installed airbag, i.e., dueto a mechanical defect or after deployment is more than desired due bothto the absence of a trained mechanic who normally installs airbags andto the cramped quarters which prohibits the use of power tools. Thecurrent time consuming system thus requires rotation of the steeringwheel to certain positions to provide access and the unloosening andremoval of the four screws.

A number of fastener assemblies for joining two members together whichdoes not require the use of a nut are available in the prior art. Forexample, U.S. Pat. No. 5,011,355 to Motoshige discloses a pushbuttontype fastener which utilizes a stud assembly snap-fitted into one of twopanels to be joined, a mating socket being snap fit to the other panel.The two components are secured together by pushing a stud in the studassembly toward the socket. The stud assembly is released from thesocket by rotating the stud enabling a spring to urge the stud out ofits engagement with the socket.

Although the pushbutton fastener of the type illustrated in theMotoshige patent satisfactorily performs its function of releasablyjoining two panels together, the fastener requires a number ofmechanical parts to perform its function, thus increasing its cost andcomplexity. In addition, certain applications such as the airbaginstallation/maintenance procedure noted hereinabove, requires access tothe rear (non-head) portion of the fastener assembly to release it.Since the Motoshige type pushbutton fastener is releasable by rotatingthe head portion of the stud portion of the stud assembly, it would notbe adaptable for use in that application.

What is therefore desired is to provide a pushbutton, or press fit, typefastener for releasably joining together two panels which is lesscomplex, less expensive and wherein the fastener can be released byaccessing the fastener at the end opposite the head of the stud.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a fastener assembly for securing a firstpanel member to a second panel member in a spaced apart relationship.The fastener assembly comprises a tubular shank portion having first andsecond end portions and a cavity formed in said shank portion. A firstspring member is secured on the outside of the shank portion, the shankportion having openings formed to enable hardened steel ball members toprotrude therefrom. Inside the shank portion cavity is a stepped pinmember spring loaded and held in place by a combination of the shankportion spring ball retention feature and step angles formed on the pinmember. The ball members are in the retracted position until usage, heldthere by a first spring member. When the fastener is pushed into anaperture formed in the second panel member, the first spring member iscompressed back toward the first end of said shank portion and movesaway from the ball members it normally forces inward. As the fastenerpasses through the aperture, the ball members are still in the retractedposition since the aperture diameter is approximately the same size asthe inside diameter of the first spring member that previously containedit in the shank openings. When the fastener pushes through the apertureand beyond the ball members, a second spring member, positioned behindthe pin member, pushes the pin forward and forces the ball members toexpand radially, thus securing itself to the second panel membercompleting the installation. At this point, there is a compressive loadbetween the retracted first spring on the panel member and the radiallyexpanded locked ball members. To remove the fastener, a tool is insertedin a recess formed in said pin member and the pin is pushed axiallybackward toward the first end of said shank portion, compressing thesecond spring member and allowing the ball members to retract inwardly.As the ball members are retracted to the proper depth, the fastenerexits the hole due to the compressed first spring ejection load and thefirst panel member is free to be removed. Simultaneously, the firstspring member positions itself over the ball members to maintain them inthe retracted position.

The present invention thus provides a novel pushbutton type fastenerthat requires fewer components and wherein the panels joined together bythe fastener can be quickly released by accessing the fastener at theend opposite its head portion, a feature required in many applications.

The reduction in the number of components necessary to fabricate thefastener of the present invention increases reliability of the fastenerwhile reducing its fabrication cost.

DESCRIPTION OF THE DRAWING

For a better understanding of the invention as well as other objects andfurther features thereof, reference is made to the following descriptionwhich is to be read in conjunction with the accompanying drawingwherein:

FIG. 1 is an assembly view of the fastener of the present invention;

FIG. 2 illustrates the fastener of the present invention utilized tosecure an air bag support plate member to a vehicle steering mountingsupport; and

FIGS. 3(a) through 3(c) illustrate the steps of securing two platemembers together and FIG. 3(d) illustrates how the two plate members arereleased; and

FIGS. 4(a) and 4(b) illustrate another embodiment of the fastener of thepresent invention.

DESCRIPTION OF THE INVENTION

Referring now to the figures, an assembly view of a pushbutton typefastener 10 according to the present invention is illustrated in FIG. 1.While pushbutton fastener 10 can be utilized to join together varioustypes of members, one important application is that shown in FIG. 2wherein an air bag support plate member 12 is secured to a vehiclesteering wheel support member 14, member 14 supporting steering wheel 16via plate member 17. As has been noted hereinabove, it has beendetermined that for installation and repair purposes it is advantageousto enable access to the fastener 10 through its rear, or non-headportion end, due to the nature of the airbag installation.

Fastener 10 comprises a stud 11 having a head 20 and a shank portion 22with probe end 23, shank portion 22 having a hollow portion, oraperture, 24 formed therein as illustrated. A plurality of openings 26(although only two holes are illustrated, one or more holes could beprovided) are formed in the shank portion 22. Positioned within theholes are corresponding hardened steel balls 28. Compression springmember 30 is formed around the outside surface of shank portion 22. Asillustrated in FIG. 3(a), spring 30 is designed to have a portion 32wherein the coils are diagonally wrapped around the shank portion andhaving a predetermined distance between each coil and a portion 34wherein the spring members are formed in a close pattern about the holes26 formed in the shank portion as illustrated. In this area of shankportion 22, the spring coils are adjacent to one another and the axisthereof is substantially aligned with the axis of the fastener 10 asillustrated. It should be noted that there is a section 21 under head 20that is pressed into the panel member 12 securing the head of thefastener 20 to the panel member 12. It should be noted that head 20 andsection 21 can be replaced with alternate configurations depending onthe particular application for fastener 10, the only requirement beingthat a surface of sufficient dimensions be provided to engage one end ofspring portion 32 since spring member 30 must be held in place on shankportion 22 during the fastener installation/removal process. Thisrequirement can be met with a surface which is an integral part offastener 10 or, for example, by a separate, adjacent plate member.Positioned within aperture 24 is a stepped pin 35 loaded (compressionforce applied thereto) by internal spring 37. Pin 35 comprises a seriesof cylindrical step portions 36, 38, 40 and 42 of differing diameters,joined by angled, or stepped, surface portions 44, 46 and 48,respectively, as illustrated. A hollowed end portion 49, or recess, incylindrical portion 42 is provided to enable a driver access thereto forthe reasons set forth hereinafter. Pin member 35 is loaded by spring 37and held in place within aperture 24 by angular step 44 resting againstball members 28 (FIG. 3c).

Ball members 28 are in the retracted position until usage, held there inplace by portion 34 of spring 30. When fastener 10 is inserted into theaperture in panel member 14 as shown in FIG. 3(b), spring 30 iscompressed back toward the head 20 of the fastener and moves away fromball members 28 it was initially forcing inward as shown in FIG. 3(a).As fastener 10 passes through aperture 15 formed in panel 14, the ballmembers are still in their retracted position because the diameter ofthe hole is approximately the same size as the inside diameter of spring30 that once contained it. When fastener 10 passes completely throughthe aperture in panel 14 as shown in FIG. 3(c), spring portion 37 pushesthe pin forward (in the direction of arrow 60), forcing the ball members28 to expand in the radial direction thus securing the fastener to thepanel member 14. As illustrated in FIG. 3(c), the spring 30 is nowsubstantially compressed and internal spring 37 in its expandedposition, pin member 35 being forced towards the probe end 23 of theshank portion of fastener 10. At this point, the bottom surface of thespherical ball members 28 are in contact with the surface of cylindricalportion 38 and angled surface 44 such that the ball members 28 have beenforced to protrude from openings 26. The diameter of cylindrical portion38 is selected such that ball members 28 protrude sufficiently to securethe fastener to panel member 14 yet provides enough available materialadjacent openings 26 when the edges are staked to retain the ballmembers within aperture 24 notwithstanding large axial forces applied topin 35. At this point spring 30 applies a compressive force (pre-load)to the rear surface of panel member 14 and the radially expanded lockedball members 28. It should be noted that during the initial fabricationof the fastener 10, the holes 26 in the shank portion 22 are firstformed of a diameter greater than a diameter of the ball members 26. Theinternal spring member 37 and the pin member 35 are then placed in theaperture 24 within the shank portion 22 and the ball members 28 are thenplaced in the apertures in the position shown in FIG. 3(a). At thispoint a staking tool is used to reform, or stake, the edges of the holes26 in an amount such that portion 27 of the holes 26 are smaller thanthe diameter of the ball members 28 thus preventing the ball membersfrom exiting through the holes they are in, completing the installation.In order to remove plate member 12, a driver tool 63 is positioned inrecess 49 of pin 35 and pin 35 is pushed axially toward head 20 in thedirection of arrow 64 as shown in FIG. 3(d). This action compressesspring 37 and enables the balls 28 to move down the angled surface 46adjacent cylindrical portion 40. This action is aided by compressionspring 30 which also as, due to its ejection load, to move the fastenerin the direction of arrow 64 and thus to automatically eject thefastener panel member 14. As the ball members 28 retract to the properdepth, fastener 10 is ejected from the hole in panel member 14 enabling,in the application described, the airbag unit attached to support plate12 to be removed. As the fastener is ejected, spring member 30 positionsautomatically itself over ball members 28 to maintain them in theretracted position, enabling the fasteners to be reused.

It is apparent that the inner stepped pin 35 in the embodiment shown inthe previous figures is restrained from exiting aperture 24 by theinterference of the ball members 28. As described hereinabove, the ballsare captivated to the fastener by a staking process on the exteriorshank portion of the pin. The location of the stepped pin against theball can result in a major mechanical advantage causing the ball members28 to be ejected from openings 26 if a sufficient load is appliedaxially to the inner stepped pin 35 when the airbag detonates. This loadcan force the balls radially outward and against the captivating stakingportion, pushing the staked material away and allowing the ball members28 to leave its original confines and also allowing the inner steppedpin 35 and spring 37 to exit their original location within aperture 24.

Referring now specifically to FIGS. 4(a) and 4(b), the radial loading ofthe ball members 28 are eliminated by removing the inner pin retainerstep portion 36. (The same reference numerals utilized in bothembodiments describe identical components). FIG. 4(a) illustrates thecaptivating step of the installation process with ball memberscontacting cylindrical portion 38' (equivalent to FIG. 3(c)), FIG. 4(b)illustrating the release step with ball members 28 forced into thevalley between surface portions 46 and 48, (equivalent to FIG. 3(d)).Therefore, any axial load or impact cannot affect the dislodging of theball members 28. In this embodiment, the ball staking process is onlyconcerned with just holding the ball members 28 in place and not theeffect of the inner pin step member 44 reacting on it. To prevent thepin member 35 and spring 37 from exiting the pin, it is captivated byforming additional material, at the end of aperture 24 to a diameterthat is smaller than the diameter of the pin member 35. As shown in thefigures, the chamfered end 23 of the fastener has an angled portion 70,the resulting aperture diameter at this end of the fastener beingsmaller than the diameter of step portion 42. What is significant is theamount of material that can be used to captivate the pin member 35 whichhas considerably more mass than the ball staking process which issomewhat limited in displacing material. Also, the opportunity to createany mechanical advantage to activate the removal of the pin member 35 iseliminated by removing the pin retainer angular step 44 and extendingcylindrical portion 38 to form cylindrical portion 38' as illustrated.

An additional technique for minimizing the radial type forces applied toball members 28 if large axial forces are applied to pin member 35 is toincrease the diameters of aperture 24 and cylindrical portion 36 andincrease the angle of inclined portion 44. In this configuration, thecontact point of the ball members 28 is such that the primary forceapplied thereto forces the ball members against the adjacent end portion29 (FIG. 3(c)) instead of radially outward.

For the application noted hereinabove, the present invention allows anoperator to quickly install the airbag unit from the driver's side,probe end 23 being chamfered to allow easy alignment. The operator takesthe airbag assembly on panel 12 and presses it towards the matchingplate where the fasteners are inserted into the mating holes. As theoperator continues to push inward toward the steering wheel, an audibleclick is heard which signifies installation is complete. In thisapplication, the fastener of the present invention does not require thesteering wheel to be rotated. To remove the unit, a small diameter tool,like a crosspoint screwdriver, simply be inserted into the end of thefastener opposite the head to engage the center pin therein. When thecenter pin is pushed or depressed, the ball members retract and theouter spring assists in the quick ejection of the steering wheel plate.What is more important, no rotational loosening or tightening isrequired because there are no threaded portions. In contradistinctionthereto, current procedure requires the operator to rotate the steeringwheel, use special tools and work behind the wheel and dashboard screwsfor assembly. The operator must first locate and then install four andremove screws and their associated nuts.

Although particularly adapted for use in airbag installations asdescribed above, the fastener of the present invention can be used inother applications requiring pushbutton type fasteners, the pushbuttonfastener of the present invention being less complicated and lessexpensive than prior art devices because there are fewer parts requiredfor its operation. The release operation is very simple and as notedhereinabove and is accomplished by accessing the far end of thefastener, an arrangement which is required in many applications. Inaddition, after release, the fastener is available for reuse in thefield.

While the invention has been described with reference to its preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt to aparticular situation or material the teaching of the invention withoutdeparting from its essential teachings.

What is claimed is:
 1. A push button type fastener comprising:anelongated shank having a first end terminating in a second end spacedfrom said first end; means defining an aperture extending inwardly fromsaid second end of said elongated shank along the longitudinal axis ofsaid elongated shank; means defining an opening in said elongated shankthat connects said aperture to the outside surface of said elongatedshank; a retention member, having first and second surface portion,positioned in said opening; a first spring positioned about the outsidesurface of said elongated shank, wherein said first spring has a firstportion positioned in contact with said first surface portion of saidretention member; a pin positioned within said aperture; a second springapplying a compressive force to said pin, wherein said pin has an endfacing said second end of said elongated shank and is in contact withsaid second surface portion of said retention member.
 2. The fastener asset forth in claim 1 wherein said pin comprises a plurality ofcylindrical portions of differing diameters, each cylindrical potionbeing separated by an angled surface.
 3. The fastener as set forth inclaim 1 wherein the first portion of said first spring that is incontact with the first surface portion of said retention member forcessaid pin into a retracted position wherein first surface portion of saidretention member is substantially coextensive with the surface of saidshank.
 4. The fastener of claim 1 wherein the first surface portion ofsaid retention member protrudes from said opening when the first portionof said first spring is removed from contact with the first surfaceportion of said retention member.
 5. The fastener of claim 4 wherein thesecond surface portion of said retention member is in contact with thesurface of one of the cylindrical portions of said pin afterinstallation of the fastener in a panel.
 6. The fastener of claim 5wherein the second surface portion of said retention member is incontact with an angled surface of said pin when the first portion ofsaid first spring is removed from contact with the first surface portionof said retention member, the largest diameter of the second angledsurface being greater than the largest diameter of first angled surface.7. The fastener of claim 1 wherein said retention member comprises aspherical ball.
 8. The fastener of claim 7 wherein the diameter of saidopening adjacent the surface of said elongated shank is less than thediameter of the spherical ball.
 9. The fastener of claim 1 wherein saidpin has a recessed end accessible through said aperture for receiving afastener release tool.
 10. The fastener of claim 1 wherein the diameterof said opening adjacent the surface of said elongated shank is lessthan the diameter of said opening adjacent said aperture.
 11. Thefastener of claim 1 wherein the first portion of said first spring is incontact with said retention member after the fastener is released from apanel.
 12. A push button type fastener comprising:an elongated shankhaving a first end, a second end opposite the first end, and meansdefining an aperture extending into said elongated shank from the secondend along the longitudinal axis of said elongated shank, means definingan opening in said elongated shank, near the second end of saidelongated shank, that extends through said elongated shank to theaperture; a retention member positioned in said opening, wherein saidretention member is movable between a locked position and retractedposition; first spring means encircling said elongated shank and havinga first portion disposed adjacent to the second end of said elongatedshank and a second portion opposite the first portion, wherein saidfirst spring means is movable between a compressed position and anexpanded position; holding means disposed adjacent to the first portionof said first spring means for holding said retention member in theretracted position when said first spring means is in the expandedposition; a pin axially positioned within the aperture in contact withsaid retention member, wherein said pin is axially movable between aretracted position in which said first spring means is in the expandedposition and said holding means is holding said retention member in theretracted position, and a forward position in which said first springmeans is in the compressed position and said retention member is in thelocked position; and second spring means for biasing said pin to theforward position and wherein said holding means and said first springmeans is a single coil spring.
 13. The fastener of claim 12 wherein thediameter of the aperture at the second end of said elongated shaft isless than the diameter of that portion of said pin accessible throughthe aperture.
 14. The fastener of claim 12 wherein said pin has arecessed end accessible through said aperture for receiving a fastenerrelease tool.
 15. The fastener of claim 14 wherein the fastener isreleased when the retention member assumes its retracted position uponapplication of sufficient force to said pin by a fastener release tool.16. The fastener of claim 12 wherein the first end of said elongatedshank terminates in a spring retainer.
 17. The fastener of claim 16wherein said first spring means applies force to the spring retainer toassist in the release of the fastener from a panel.
 18. The fastener ofclaim 12 wherein said holding means is a plurality of coils in closeproximity with one another that extend from the first portion of saidfirst spring means. .Iadd.
 19. In combination with an automobile air bagmodule, an air bag fastener assembly comprising:an air bag support platehaving opposing front and rear faces and an aperture therethrough; anelongated shank attached to the air bag module, the elongated shankbeing formed with an interior and including a probe end movable throughthe aperture in a first direction past said front face of said supportplate, and the probe end of said elongated shank being formed withopenings extending through said elongated shank to said interior;opposing first and second retention members located within the interiorof said shank; and a resilient device acting to bias said retentionmembers to extend through said openings to locations outside of saidelongated shank, for engaging said rear face of said support plate,whereby said probe end is prevented from moving through said supportplate in a second direction, opposite to said first direction..Iaddend..Iadd.20. The fastener assembly of claim 19 wherein each ofsaid first and second retention members is a spherical ball..Iaddend..Iadd.21. The fastener assembly of claim 19 wherein movement ofsaid elongated shank in the first direction past said front face of saidsupport plate causes said first and second retention members to bedisposed to engage said rear face of said support plate, to preventpassage of said probe end through said support plate in the seconddirection, opposite to the first direction. .Iaddend..Iadd.22. Thefastener assembly of claim 21 wherein:said shank further includes asprint retainer at an end opposite the probe end; said fastener assemblyfurther comprises a coil spring retained against the spring retainer andencircling said shank, extending toward the probe end; the coil springis movable between a compressed position and an expanded position; andthe coil spring applies a force to the spring retainer as the fastenerassembly is released, to thereby assist in the release of the fastenerassembly from the air bag support plate. .Iaddend..Iadd.23. The fastenerassembly of claim 19 wherein: said elongated shank defines alongitudinal axis; said resilient device includes a spring devicelocated within the interior of said elongated shank; said first andsecond retention members are biased radially outward by said resilientdevice to extend substantially perpendicular to the longitudinal axis ofsaid elongated shank, through said openings to locations exterior ofsaid elongated shank; and wherein movement of said shank in the firstdirection past said front face of said support plate causes saidretention members to be disposed adjacent to said rear face of saidsupport plate, to prevent passage of said probe ends through saidsupport plate, in the second direction, opposite to the first direction..Iaddend..Iadd.24. The fastener assembly of claim 19 wherein saidresilient device is a spring. .Iaddend..Iadd.25. The fastener assemblyof claim 19 wherein said openings are two in number, and are arrangeddiametrically opposite each other. .Iaddend..Iadd.26. The fastenerassembly of claim 19 wherein:said elongated shank includes a springretainer that is positioned adjacent to a head end of the shank,opposite the probe end; and said fastener assembly further comprises acoil spring that is compressed between the support plate and the headend upon insertion of said elongated shank through said support plate,the retention members preventing the bias of the coil spring fromremoving the elongated shank from said aperture until said retentionmembers are compressed radially inward by a predetermined amount..Iaddend..Iadd.27. The fastener assembly of claim 26, wherein: the coilspring also normally biases the first and second retention membersradially inward, such that they together fit through the aperture; andthe coil spring can be selectively compressed to cause the first andsecond retention members to be urged radially outward, such that they donot together fit through the aperture. .Iaddend..Iadd.28. In combinationwith an automobile air bag module, an air bag fastener assemblycomprising:an air bag support plate having first and second sides and anaperture therein with a predefined radial dimension; a shank having alength in an axial dimension, a head at one end of its axial dimension,and a probe end at the other end of its axial dimension attached to theair bag module, the probe end being axially inserted through theaperture at the first side of the support plate, the probe end havingradial dimensions such that it fits into the aperture; a coil springthat is coaxial to the shank, and that has a larger radial dimensionthan the aperture, such that the coil spring does not fit through theaperture, but is compressed between the support plate and the head endof the shank as the probe end is selectively inserted through theaperture; a resilient device; and a retention mechanism that is urged bythe resilient device to radially expand once the probe end has beeninserted through the aperture, to thereby contact the second side of thesupport plate and prevent removal of the probe end through the aperture;wherein the retention mechanism has a retracted position, in which it isradially constricted such that the retention mechanism fits into theaperture, and a locked position in which the retention mechanism isradially expanded and does not fit through the aperture. .Iaddend.